The long range goal of this project is to determine whether ambulatory blood pressure technology is useful in predicting early brain and cognitive changes that may predate stroke and other cerebrovascular pathology in healthy, elderly adults. The proposal attempts to relate 24-hour ambulatory blood pressure and heart rate to subtle brain damage assessed by magnetic resonance imaging (MRI) and associated changes. We will look at blood pressure and heart rate level and variability during two entire 24-hour periods, as well as during particular time periods or activities, e.g., morning versus other time periods, sleep versus waking, rest versus exercise, high versus low stress reported in diaries. The subjects will be 150 unmedicated men and women, between 55 and 80 years of age, with normotensive to elevated blood pressure levels. A complete medical exam will be given to exclude current disorders. Measurements will be taken of clinic blood pressure and heart rate. In addition, neuropsychological tests will sample such critical areas of cognitive functioning as memory, attention, and cognitive flexibility. We predict that, in comparison to standard clinic blood pressure measurements, ambulatory blood pressure (particularly during sleep) will be more indicate of cognitive deficits and MRI white matter and other brain changes, known as T2 hyperintensities. Normotensive and hypertensive elderly subjects with high sleeping blood pressure and heart rate values, very little decrease in ambulatory blood pressure and heart rate from waking to sleep, and large blood pressure and heart rate variability are expected to exhibit more problems with cognitive functioning and an increase in the number and severity of MRI T2 hyperintensities. If we find that elderly individuals with borderline to mild hypertension are at risk for cognitive deficit and brain damage, such results have clear implications for decisions regarding the appropriate level of blood pressure to treat in the elderly.